Feed back systems for a rotary mechanical translating device

ABSTRACT

In a rotary mechanical translating device which exhibits rotary mechanical amplification the characteristics of the translating device may be altered by negative or positive feedback. These translating devices have a power gain since they transfer power from a prime mover to an output shaft as a magnified function of the power required to rotate it&#39;&#39;s input shaft. A portion of the output is fed back through a mixing device to the input of the translating device. When the feedback is negative it reduces back lash and improves the positioning accuracy of the translating device and when the feedback is positive it increases the gain of the translating device.

Watson "[1 1 v 3,863,945 [451 Apr. 16,1974

[5.4] FEED BACK SYSTEMS FOR A ROTARY MECHANICAL TRANSLATING DEVICE [76] Inventor: Thomas A. W. K. Watson, 2720 Gover, Apt. 24, Montreal, Quebec,

Canada 22 Filed: Nov. 4, 1971 211 Appl. No.: 195,661

[51] Int, Cl. F16h 37/06 [58] Field of Search 74/675 [5 6] References Cited UNITED STATES PATENTS 2,128,477 8/1938 Schlosser, Jr. 74/675 2,207,866 7/1940 Kriek 74/675 X 2,310,115 2/1943 Pop0ff.. 74/675 2,363,201 11/1944 Popolf 74/675 2,384,776 9/1945 Trofimov 74/689 2,476,266 7/1949 Trofimov 74/675 X 2,531,611 11/1950 Canfield 74/675 X 2,847,876 8/1958 Willard 74/751 2,924,991 2/1960 Whiting 74/675 H1967 Twiford 74/682 FOREIGN PATENTS OR APPLICATIONS 1,114,220 12/1955 France 74/675 Primary Examiner-Allan D. I-Ierrmann Assistant ExaminerP. S. Lall 57 2 ABSTRACT the feedback is positive it increases the gain of the translating device.

4 Claims, 11 Drawing Figures PATENTEDAPR 16 m4 SHEET 2 BF 2 FIG IO Rotary mechanical translating devices capable of rotary mechanical amplification are described in my U.S. patent application entitled Rotary Mechanical Translating Device, Ser. No. 94,819, filed Dec. 3, 1970 and also in my patent application entitled Rotary Mechanical Translating Devices employing Rotary Releasers, filed June 30, 1971, Ser. No. 158,250. Also a feedback system is shown in my patent application entitled Constant Mesh Automatic Transmission, filed Dec. 3, 1970, Ser. No. 94,818, and now abandoned.

This inventionrelates to feedback as applied to rotary mechanical translating'devices which exhibits rotary mechanical amplification. It is directed toward negative and positive feedback systems which alter the operating characteristics of the translating devices.

Feedback has been previously applied to Electronic, ElectricaLl-Iydraulic and Servo amplifiers. Application of feedback to these amplifiers alters their gain, time response, positioning accuracy, etc. A translating device has a control input shaft, an output shaft which is connected to a load and a prime mover shaft to which is connected a prime mover. The term input will refer to the translating devices control input shaft and term output to its output shaft. The translating device transfers power to its output shaft only when the input shaft is rotated. Feedback is accomplished by sensing the amount of rotation of the output shaft and feeding a portion of this rotation back to its input. In this arrangement the control input shaft'of the system which will be referred to as the mixer input is connected to a mixer or comparator which in turn drives the input of the translating device. The feedback from the output is also fed into this mixer. The mixer in the case of negative feedback subtracts the feedback output rotation from the mixer input rotation thereby reducing the overall input to the translating device. In the case of positive feedback it adds to the input.

Since negative feedback reduces the input to the translating device it lowers its amplification. It however improves the positioning accuracy of the device by comparing the angular position of the output and the mixer input andfeeding an error or difference angle back to the translating devices input. When the output lags behind the input the feedback is less than if it followed the input, hence the greater the lag the less the negative feed back and the more the translating device is driven in order to compensate for the error. This reduces the positioning error due to back lash and the system s elasticity. It also reduces over shoot caused by the system s inertia, since the translating device is decelerated by the increased negative feedback, as a result of the output leading the input. It also reduces jitter by opposing variations which manifests themselves as a difference betweenthe input and the output of the mechanical amplifier system.

Positive feedback has the opposite effect of negative feedback. lt increases system error,'over shoot, jitter and gain. It is therefore basically useable as a menas of increasing a translating devices gain.

Feedback may be used over several stages of mechanical amplification with similar results.

Since relatively small precision components may be employed in the feedback loop as compared with the output portion of the mechanical amplifier system,

back lash, inertia and elasticity in the feedback loop maybe held to a minimum. This makes it possible to take full advantage of feedback without introducing additional problems as a result of weaknesses in the feedback loop. I

There are two basic types of rotary mechanical translating devices, linear and nonlinear. In a linear system the output follows the input except for minor variation due to back lash, inertia and elasticity, hence feedback can only correct these difficulties. In nonlinear rotary mechanical translating devices the output does not necessarily follow the input. The output is determined by the transfer characteristics of the translating device and the speed torque characteristics of the prime mover which drives the translating device. Negative feedback applied to a nonlinear translating device can be employed to provide ,the mechanical amplifier system with a relatively constant speed or constant torque characteristic.

The torque speed characteristics of the output of a nonlinear device for a constant speed input is dependent on the prime movers torque speed characteristics. By employing negative speed feedback a relatively constant speed characteristic will result. If the load is increased this decreases the output speed as a consequence of the prime movers speed dropping. The amount of angular rotation fed back to the input will therefore decrease. Since the mixer input speed to the system is held constant and the amount of rotation fed back to the mixer or comparator is reduced the input speed will increase resulting in an increase in the output speed of the translating device. Since the output speed is raised back to nearly its original speed a relatively constant speed characteristic is produced. The prime mover must be capable of delivering the additional power required by the load. 7

A torque sensing device maybe inserted in series with the output shaft of a nonlinear translating device. The torque sensing devices rotates an output shaft in proportion to the developed output torque and speed. As the torque increases so does the sensing devices output speed increase, however this speed is limited by the translating devices output speed. The output of this torque sensing devices is negatively fed back through a mixer to the input of the translating device and will produce a mechanical amplifier system having a relative constant torque. As the'output torque increases due to loading so does the amount of feedback which will reduce the input speed of the translating device. This in turn reduces the output speed of the translating device resulting in it reducing the loading effect on the prime mover driving the translating device.

Speed sensing the output angular velocity of a translating device and positively feeding back the sensed speed to the input of the translating device, will also produce a relatively constant torque characteristic. in this system'as the outputs angular velocity drops due to loading so does the amount of positive feedback which in turn reduces the input speed of the translating device. This reduces the loading of the driving prime mover again resulting in the system having a relatively constant torque.

Feeding backthe sensed torque positively, such tha as the torque increases, the input speed of the nonlinear translating device is increased, will result in a relatively constant speed characteristic. As the load increases so does the torque, which increases the output speed of the torque sensing devicewhich is fed back to add to the input speed. When the output is loaded the torque increases, the prime mover speed drops due to loading and the input speed to the translating device is increased compensating for the drop in the prime mover speed. This will further load the prime mover. This system will only function up to the condition where the prime mover is capable of delivering the additional power demanded by the load.

Torque sensing the output of a linear translating device and feeding it back negatively as was done with the nonlinear translating devices will cause the output speed of the system to decrease with loading. This will reduce the loading of the prime mover allowing the system to produce a relatively constant torque output with poor speed regulation. The linear translating device is a constant speed device and has excellent speed regulation as compared to the nonlinear translating device.

Torque sensing the output of a linear translating device and feeding it back positively as was done with the nonlinear translating devices will cause the output speed of the system to increase with loading. The linear translating device has a constant speed characteristic hence its output speed will be at a minimum at zero torque and will increase as the positive feedback increases with a rise in output torque. Again the prime mover must be capable of supplying the additional power required.

In the feedback systems using speed sensing the feedback will be linear provided no slipping occurs in the feedback loop. Gearing will transfer a true reproduction of the variations in output speed back to the input, hence producing linear feedback. When a pulley and belt arrangement is used to feedback variations of the output back to the input, slippage could occur and the system would become nonlinear.

The feedback systems using torque sensed feedback could be linear or nonlinear. The linearity of the feedback is dependent upon the design of the torque sensing device and is not necessarily dependent upon the system of torque sensing used.

Nonlinear speed feedback maybe accomplished by inserting a nonlinear device in the feedback loop of the rotary mechanical amplifier system. A nonlinear translating device maybe used for this purpose.

Nonlinear feedback maybe very desireable when it is required to modify the speed torque characteristics of a prime mover.

An objective is to provide a feedback means for rotary mechanical translating devices.

Another objective is to provide a negative feedback means for rotary mechanical translating devices.

Another objective is to provide a positive feedback means for rotary mechanical translating devices.

Another objective is to provide a speed feedback means for rotary mechanical translating devices.

Another objective is to provide a torque feedback means for rotary mechanical translating devices.

Another objective is to provide a nonlinear feedback means for rotary mechanical translating devices.

Still another objective is to provide a means of reducing backlash and jitter in rotary mechanical translating devices.

Another objective is to provide a means of improving the positioning accuracy of a rotary mechanical translating device.

Another objective is to provide a relatively constant speed characteristic for nonlinear rotary mechanical translating devices.

Another objective is to provide a relatively constant torque characteristic for nonlinear rotary mechanical translating devices.

Another objective is to modify the speed and torque speed characteristic of linear rotary mechanical translating devices.

These and other objectives will become apparent in the description that follows:

FIG. 1 is a schematic diagram of a rotary mechanical translating device with a negative speed feedback loop.

FIG. 2 is a schematic diagram of a means of converting the arrangement shown in FIG. 1 to positive feedback.

FIG. 3 is a schematic diagram of a linear rotary mechanical translating device capable of rotary mechanical amplification in one direction with positive feedback.

FIG. 4 is a schematic diagram of a means of converting the arrangement shown in FIG. 3 to negative feedback.

FIG. 5 is a schematic diagram of a linear rotary mechanical translating device capable of rotary mechanical amplification in two directions with a feedback loop.

FIG. 6 is a schematic diagram of a nonlinear rotary mechanical translating device with negative feedback.

FIG. 7 is a schematic diagram of a means of converting the arrangement shown in FIG. 6 to positive feed back.

FIG. 8 is a schematic diagram of a rotary mechanical translating device with torque sesning positive feedback.

FIG. 9 is a schematic diagram of a means of converting the arrangement shown in FIG. 8 to negative feedback.

FIG. 10 is a schematic diagram of a rotary mechanical translating device with nonlinear speed positive feedback.

FIG. 11 is a schematic diagram of a means of converting the arrangement shown in FIG. 10 to negative feedback.

FIG. 1 shows a rotary mechanical translating device 1 with an input or control shaft 3, a prime mover shaft 4 and an output shaft 5. A gear 6 is attached to shaft 5 and meshes with gear 12 on shaft 11 attached to an end gear of differential 10. Gear 9 is connected to the spider of differential 10 and meshes with gear 13 attached to shaft 14. Shaft 8 is connected to another end gear of differential 10. A gear 7 is fixed to shaft 8. Gear 7 meshes with gear 2 fixed to shaft 3. A self locking worm l6 and worm gear 15 are meshed, gear 15 is attached to shaft 14 and worm 16 is attached to the mixer input shaft 17.

Translating device 1 provides mechanical amplification. A prime mover is attached to shaft 4. Input shaft 3 controls the amount of rotary power transfered from the prime mover to the output shaft 5. A portion of the angular displacement of shaft 5 is fed back to the input shaft 3, through the gears 6 and 12, differential 10 and gears 7 and 2. Differential 10 acts as a mixer or comparator and shaft 17 becomes the mixer input shaft. A load is normally connected to shaft 5.

- The arrows in FIG. 1 shows the-relative direction of rotation of the shafts for negative feedback. It is assumed that rotation of shaft llwill cause shaft 8 to rotate in the opposite direction, as a result of the action of differential 10. Had the feedback been made via gear 9 attached to differential ls spider; the direction of the feedback as applied to shaft 8 would have not been reversed. In this case shaft 11 would become the mixer input shaft.

In operation, the sequence of events areas follows rotation of shaft 17 will result in the rotation of gear 9 which will drive shaft 8. Shaft 11 instantaneously is not driven since it offers a greater resistance to rotation, as a result of being coupled through gears 12 and 6 to theoutput load however shaft 11 will rotate an instant later. When shaft 8 rotates it drives shaft 3 which permits the translating device 1 to transfer power from the prime mover shaft 4 to the output shaft 5 causing it to rotate. The rotation of shaft 5 drives shaft 11 through gears 6 and 12. Shaft 11 drives shaft 8 through differential 10, but in the opposite direction to which it is driven by the rotation of shaft 17. This is a negative feedback system. The amount of feedback is dependent upon the speed transfer characteristic of the translating device 1 and the ratio of gears 6 to 12 and 7 to 2, also the differential ratio which is normally one to one.

If the output shaft 5 does not follow shaft 3, as is often the case with non linear translating devices when their output loading is increased, and lags shaft, the feedback through shaft 1 1 and differential to shaft 8 will be reduced. This will have the effect of increasing the amount of rotation of shaft 8 and input shaft 3. Shaft 5 will then be further driven by the translating device 1 hence increasing its angular velocity, thereby reducing the difference between its angular velocity and that of shaft 17.

If the output shaft 5 over shot it would lead, that is it would momentarily increase its speed relative to that of shaft 17. Over shoot of shaft 5 will occur when shaft 17 is decellerated due to the inertia present at shaft 5. This would increase the feedback and consequently reduce the drive to the translating device 1, thereby reducing its lead. I The input worm 16 and worm gear are not always necessary. They prevent the spider gear 9 from freely rotating which could effect the feedback ratio. Shaft 14 could be connected to a system which resists its easy rotation.

The negative feedback system in FIG. 1 will reduce jitter, backlash and over shoot in linear translating devices. ln non linear translating devices, it will reduce jitter, backlash and over shoot, it also produces a relatively constant speed characteristic.

FIG. 2 shows a gear 15 on shaft 5 meshing with gear 16'. Gear 16' meshes with gear 17' on shaft 11. Gear 15', 16 and 17' maybe substituted for gears 6 and 12. This will change the sense of the feedback from negative as shown'in FIG. 1 to positive.

In this configuration the sequence of events is such that rotation of the input shaft 17 results in the rotation of shaft 8 and shaft 3 which controls the translating device l. Shaft 5 rotates when shaft 3 is driven causing gear 15 to drive gear16' and gear 16' to drive gear 17. This results in the rotation of shaft 11 which further drives shaft 3 through the differential 10. In this system the feedback is positive since the output helps drive the input, increasing the systems gain. It also produces a relatively constant torque characteristic. If the speed of shaft 6 drops due to loading, so will the amount of feedback through differential 10 back to shaft 3 be reduced. This further reduces the speed of shaft 3, thus allowing it to deliver a relatively constant torque, since this reduces the loading effect on the prime mover.

The feedback ratio is determined by the gears 15, 16 and 17', differential 10 and gears 2 and 7. The feedback ratio should not be made unity since if the speed gain transfer characteristic of the translating device is also unity, the system will continuously rotate.

FIG. 3 shows a differential 20 having its end gears connected to shafts 22 and 26 and its spider to gear 21. Shaft 27 is connected to self locking worm 25 which meshes with worm gear 24. i Worm gear 24 is connected to shaft 26. Bevel gear 28 is attached to shaft 27 and mesheswith bevel gear 29 attached to shaft 30. Shafts 30 and 33 are'connected to the end gears of differential 31 whose spider is connected to gear 32. A shaft 42 is connected to gear 41 and meshes with gear 21 which in turn meshes with gear 32.

This portion of FIG. 3 acts as a linear rotary mechanical translating device which exhibits mechanical amplification having an input shaft 33, an output shaft 22 and a prime mover shaft 42. i

Gear 23 is fixed to shaft 22 and meshes with gear 35 attached to the spider of differential 34. Shafts 33 and 36 are connected to the end gears of differential 34. Shaft 36 is connected to self locking worm gear 37 which meshes with worm 38 attached to the mixer input shaft 39.

Gears 23 and 35 feedback output rotation of the output shaft 22 to the input shaft 33.

In operation a prime mover drives differentials 20 and 31. Differential 211 tends to drive shafts 22 and 26. The rotation of shaft 26 is restricted by the self locking worm 25 and worm gear 24. Differential 31 drives shaft 30 gears 29, 28, 25 and 24 and shaft 26 of differential 20. The ratio of these gears is selected such that if shaft 33 is held stationary, shaft 22 will not rotate. This ratio is usually unity. When shaft 33 is rotated in the direction shown it reduces the drive to'shaft30 due to the action of differential 31 resulting in shaft 30 reducing its speed, hence that of shaft 26. Shaft 22 will then ro-. tate as a result of the action of differential 20 being driven by the prime mover. Some torque from shaft 22 will be transfered through the differential 34 via gear 23 to shaft 36 tending to drive the worm gear 37 against worm 38. Shaft 39 acts as the mixer input shaft to the system driving shaft 36 through worm 38 and worm gear 37. Worm 33 and worm gear 37 may be eliminated if the system to which shaft 36 is connected prevents its easy rotation. The translating device shown in FIG. 3 rotates only in one direction. It may be reversed by reversing the direction of the prime mover. It is linear in as much as the output always follows the input. 7

The feedback in the system of FIG. 3 is positive. When shaft 39 is rotated, shaft 36 rotates causing the rotation of shaft 33, which results in the rotation of shaft 22 due to the translating devices action. Gear 23 then drives gear 35'adding to the rotation of shaft 33 thereby increasing the systems gain.

FIG. 4 shows a gear 40 mounted on shaft 22 and meshing with gear 41. Gear 41 is meshed with gear 35 attached to differential 34. When gear 40 and 41 are substituted for gear 23 they reverse the sense of the feedback, hence this arrangement has negative feedback.

FIG. shows a differential 54 having shafts 52 and 57 attached to it's end gears and gear 55 to its spider. Gear 53 meshes with gear 55 and is attached to shaft 56. Self locking worm 51 and worm gear 50 are meshed. Worm 51 is connected to shaft 62 and worm gear 50 is connected to shaft 52. Differential 63 has shafts 62 and 77 attached to it's end gears and gear 64 to its spider. Gear 64 meshes with gear 65 to which is attached shaft 66. Gear 67 meshes with gears 65 and 70.

Differential 69 has shafts 68 and 87 attached to its end gears and gear 70 to its spider. Self locking worm 59 ismeshed with worm gear 58 attached to shaft 57. Shaft 68 is attached to worm 59. Worm 78 meshes with worm gear 79 attached to shaft 77. Worm 78 is attached to shaft 80. Differential 81 has shafts 80 and 84 attached to its end gears, and gear 82 to its spider. Gear 83 is attached to shaft 88 and is meshed with gear 82. Self locking worm 86 meshes with worm gear 85, attached to shaft 87. Worm 86 is attached to shaft 84.

This section of FIG. 5 is a rotary translating device in which shaft 88 acts as an input shaft, shaft 56 as an output shaft and shaft 66 as a prime mover shaft.

Bevel gear 60 meshes with bevel gear 61 and is attached to shaft 56. Shaft 71 is attached to bevel gear 61. Differential 72 has shafts 71 and 76 attached to its end gears and gear 75 to its spider. Gear 73 meshes with gear 75 and is attached to shaft 74. Shaft 76 is attached to bevel gear 90 meshed with bevel gear 89, attached to shaft 88. Bevel gear 91 may be used in place of gear 89. It is also attached to shaft 88 and meshes with bevel gear 90.

A prime mover is connected to shaft 66 and drives differential 63 and 69, which in turn drives worms 51 and 59 respectively. Worm 51 and 59 drive worm gears 50 and 58 respectively, and in turn drive differential 54. The drive to differential 54 is balanced such that shafts 52 and 57 rotate in the opposite direction to each other with the same angular velocity. As a result of this balanced drive, the spider of differential 54 or gear 55 does not rotate. When shaft 88 is rotated in one direction it rotates shaft 84, which causes shaft 87 to rotate, which will reduce the speed of rotation of shaft 68 on the other side of differential 69. This upsets the balanced drive to differential 54, resulting in gear 55 rotating. Rotating shaft 88 in the opposite direction will result in unbalancing differential 54 in the opposite direction. operationally power is transferred from a prime mover connected to shaft 66 to shaft 56 as a result of unbalancing the translating device, by rotating shaft 88. Shaft 80 is easy to rotate in the direction which it is tended to be driven by differential 63 through worm 78 and worm gear 79, shaft 84 is also easy to rotate in the direction it is tended to be driven by differential 69. The translating device is arranged such that shaft 80 and 84 are easily driven in opposite directions to each other, hence when shaft 88 is rotated in one direction, it selects shaft 80, and in the other di- 'rection shaft 84.

In operation when gear 89 is connected rather than gear 91 and the direction of rotations are as shown the feedback is positive. When shaft 74 is driven it will drive shaft 76 through differential 72 rather than shaft 71. Shaft 71 is the more difficult of the two shafts to drive since it would have to drive a load connected to shaft 56. Shaft 88 is driven by shaft 76 through gears 89 and 90.

Rotation of shaft 88 causes the prime mover to drive shaft 56 which in turn drives shaft 71. Shaft 71 drives shaft 76 through differential 72 in the same direction as it is driven by shaft 74, hence providing positive feedback.

If the speed transfer ratio from shafts 88 to shaft 56 through the translating device is unity and the speed transfer from shaft 56 to shaft 88 through differential 72 is unity, the system will freely rotate without mixer input to shaft 74.

Connecting gear 91 to shaft 88 rather than gear 89 will reverse'the feedback making it negative. When shaft 74 is rotated shaft 76 will rotate, hence rotating the control input shaft 88 and therefore the output shaft 56 of the translating device. Shaft 71 will be driven by shaft 56 and will tend to oppose the rotation of shaft 76.

FIG. 6 shows a tachometer 102 or a means for producing a displacement as a function of an angular velocity with an input shaft 101 and an output indicator 103. Variable speed transmission 120 has an input shaft 104, an output shaft 107 and a speed control 106. Arm 105 connects the output indicator 103 of tachometer 102 to the variable speed transmissions speed control 106. This portion of FIG. 6 forms a rotary translating device. Rotation of the input shaft 101 of tachometer 102, gives an output indication in proportion to the speed of its input shaft 101, resulting in a deflection of its output indicator or member 103, attached to arm 10 5. This adjusts the speed control 106 of transmission 120. A prime mover is connected to shaft 104. Shaft 107 is driven by shaft 104 at a speed dependent upon the setting of the speed control 106. The faster the rotation of shaft 101, the greater the deflection of indicator 103. This advances the setting of speed control 106, resulting in shaft 107 rotating at a higher speed. This type of translating device exhibits mechanical amplification since very little power is required to drive the input shaft 101 of the tachometer 102 as compared with the power delivered to shaft 107 by the prime mover. This translating device can be made to function in both directions and its linearity is dependent upon the characteristics of the tachometer, transmission and prime mover. Although it may be made fairly linear, it

is basically nonlinear when compared with the translating devices shown in FIG. 3 and 5.

Gear 108 is fixed to shaft 107 and meshes with gear 116 attached to shaft 115. Gear 100 is attached to shaft 101 and meshes with gear 109 on shaft 110. Differential 111 has shafts and connected to its end gears and gear 112 to its spider. Gear 113 attached to shaft 114 meshes with gear 112. Mixer input shaft 114 may be connected through a worm gear and a worm so as to prevent its easy rotation.

Feedback from shaft 107 to shaft 101 through the differential 111 is negative. When shaft 114 is rotated it drives shaft 110 through differential 111 rather than shaft 115. Shaft 115 is the more difficult of the two shafts connected to differential 111 to drive, as it would be required to work against any load on shaft 107. Shaft 110 drives the input shaft 101 of tachometer 102, resulting in a deflection of indicator 103. This advances the speed control 106 of transmission resulting in power being transferred from shaft 104 to shaft 107. Gear 108 drives gear 116 resulting in the rotation of shaft 115. The resulting rotation of shaft 115 reduces drive to shaft 110,-producing negative feedback. A relatively constant speed characteristic will'be obtained with this feedback system. If shaft 114 is rotated at a constant speed, and the speed of shaft 108 drops, then the amount of feedback through differential 11 1 will be reduced, speeding up shaft 101 and therefore shaft FIG. 7 shows a gear 117 mounted on shaft 107 and meshing with gear 1 18. Gear 118 meshes with gear 119 on shaft 115. This arrangement maybe connected in place of gears 108 and 116 and it will reverse the feedback. The resulting system will have positive feedback.

FIG. 8 shows a differential 131 having shafts 130 and 133 connected to its end gears and gear 132 connected to its spider. Shaft 133 is connected to the input of the translating device 145 having a prime mover input shaft 134 and an output shaft 135. Gear 136 is connected to shaft 135 and meshes with gear 161 on shaft 160. Shaft 160 rotat'es'in bearing 159 mounted to transmission housing 149. A disc 162 is fixed to shaft 160. Splined shaft 158 rotates in bearings 151 and 163 mounted to transmission housing 149. A wheel 156 is slidabley mounted to shaft 158. A bevel gear 150 which meshes with gear. 148 is fixed to shaft 158. A fork 152 which positions wheel 156 on shaft 158 is attached to rod 153. Rod 153 slides in block 154 mounted on transmission housing 149. Gear 148 is fixed to shaft 146 which rotates in bearing 146 mounted on transmission housing 149. A compression spring 157 is mounted on shaft 158, between fork 152 and bearing 163. The components enclosed byhousing 149 constitute a variable speed transmission. Gear 144 meshes with gear 132 and is attached to shaft 146. A differential 138 has shafts 135 and 139 connected to its end gears and an arm 140 to its spider. A spring 141 is attached to arm 140 and to cable 142 which runs in pulley 143 rotatably mounted to the housing 137. The components enclosed by housing 137 form a torque sensing unit. Cable 142 enters the transmission housing 149 and runs over pulley 155 which is rotatably mounted to housing 149. Cable 142 is connected to rod 153.

The system shown is torque sensing and will provide positive feedback. Rotation of the mixer'input shaft 130 results in the rotation of shaft 133 rather than gear 132, since it is assumed that the resistance offered by the transmission in housing 149 is greater than that presented to shaft 133. When shaft 133 is rotated, a

prime mover connected to translating device 145s shaft 134 drives shaft 135, which in turn drives output shaft 139 through differential 138, and also disc 1620f the transmission, via gears 136and 161. Any torque developed in the output shaft 139 creates a pull on cable 142. Cable 142 pulls rod 153 against the pressure of spring 157. The greater the torque the more the deflection of spring 157 and of wheel 156. As the torque increases so does the output speed of the transmission which is fed back to the input of the translating device via gear 144 and differential 131. This increases the speed of shafts 135 and 139 which will partially compensate for their drop in speed which normally accompanies increased loading. The system therefore provides a relatively constant speed characteristic.

If wheel 156 were positioned at point 164 on disc 162 the feedback would be negative but would decrease with increasing torque.

FIG. 9 shows a gear 165 meshing with'gears 132 and gear 166 mounted on shaft 146. When gears 165 and 166 are substituted for gear 144, the system'of FIG. 8 will exhibit negative feedback. As the output torque increases due to loading so will the speed of rotation of shaft 146 increase, which will oppose the rotation of shaft 133, thus reducing its speed, hence the speed of shaft 135. This results in a relatively constant torque characteristic, since the speed of shaft 135 will drop as its torque increases, thus partially unloading the prime mover and thereby allowing the system to maintain its torque. If wheel 156 is positioned at point 164 on disc 162 the feedback would be positive but would decrease with increasing torque.

FIG. 10 shows a differential 171 having shafts and 173 connected to its end gears. Shaft 173 is connected to the input of translating device 174,.having a prime mover input-shaft 175 and an output shaft 177. Gear 172 is attached to the spiderof differential 171 and meshes with gear 179 attached to the output shaft 180 of the variable speed transmission 181. A gear 176 attached to shaft 177 meshes with gear 183 on input shaft 182 of transmission 181. A gear 178 is attached to shaft 177 and meshes with gear 188 on shaft 187. Tachometer 189 has an input shaft 187 and a speed indicator186. An arm is connected between speed indicator 186 and the speed control 184 of transmission 181.

The tachometer senses the speed of the output shaft 177, and adjusts the speed control 184 of variablespeed transmission 181 as a function of the speed of shaft 177. Shaft 177 also drives the transmission 181. The speed of rotation of shaft 180 is then a function of the speed of rotation of shaft 182 and the setting of the control 184. The feedback path from shaft 177 to shaft 173 is through transmission 181. The amount of feedback from shaft 177 to shaft 173 is dependent upon the characteristics of the transmission and tachometer. This type of feedback can be made nonlinear by chang ing the transfer characteristics of the tachometer and transmission. The system as shown in FIG. 111 exhibits positive feedback. I

FIG. 11 shows a gear 198 meshing-with gear 172 and gear 191 on shaft 180. Gears 190 and 191 maybe substituted for gear 179 and will change the sense of feedback from positive to negative.

Although the tachometer 189 and transmission 181 form'a translating device capable of rotary mechanical amplification, they serve only to produce nonlinearity in the feedback loop and are not required to provide gain.

7 In FIG. 8 drive to the transmission could be obtained from the prime mover input shaft 134. Feedback would then be proportional to torque only and would not be effected by the speed of shaft 135. The transmission 181 of FIG. 10 may also derive its input from shaft 175, which provides another degree of flexibility for changing the linearity of the feedback.

Two or more translating devices maybe connected in cascade to provide greater amplification. The output ofthe first translating device is connected to the input of the second translation device. The output of a proceeding translating device is connected to the input of a succeeding translating device. The input to the cascaded translating devices is the input to the first translating device and the output of the cascaded translating devices is the output of the last translating device. A sin gle prime mover maybe employed to drive all the translating devices and is connected to their prime mover input connections.

Feedback maybe employed over one or more stages of cascaded translating devices. If a first and a second translating device are cascaded feedback maybe derived from the output of the second translating device and fed back to the input of the first translating device. In general, feedback maybe derived from the output of the last of a group of cascaded translating devices and fed back to the input of the first of the group of translating devices. Feedback could also be derived from the output of any one of a group of cascaded translating devices and fed back to the input of the device it was derived from or to the input of any preceding translating device. The term mixer refers to a means for producing an angular displacement which is a function of two angular displacements. A differential will perfonn this function.

I claim:

1. In an arrangement employing at least one mechanical amplifier or rotary mechanical translating device which transfers power from a prime mover to a power output shaft at a rate determined by the angular velocity of a control shaft wherein the power required to rotate the control shaft to cause said transfer of power is less than the power transferred from the prime mover to the power output shaft, a feedback system comprising a rotary mechanical translating device driven by a prime mover and having a control shaft and a power output shaft, a differential having, a first and a second and a third shaft, a coupling means for coupling a portion of the power appearing in the power output shaft to the first shaft of the differential, said second shaft of the differential connected to the control shaft of the translating device and drive means for applying an external torque connected to the third shaft of the differential.

2. A feedback system as claimed in claim 1, comprising at least a first and a last rotary mechanical translating device wherein the power output shaft of a preceeding translating device is connected to the control shaft of a succeeding translating device.

3. A feedback system as claimed in claim 1 wherein the coupling means comprises torque sensing means for detecting the torque in the output shaft, and a variable speed transmission driven by the output shaft and connected to drive the first shaft of the differential, wherein the speed transfer ratio of said transmission means is responsive to said torque sensing means.

4. A feedback system as claimed in claim 1 wherein the coupling means comprises torque sensing means for detecting the torque in the output shaft, and a variable speed transmission driven by the prime mover and connected to drive the first shaft 7 of the differential, wherein the speed transfer ratio of said transmission means is responsive to said torque sensing means. 

1. In an arrangement employing at least one mechanical amplifier or rotary mechanical translating device which transfers power from a prime mover to a power output shaft at a rate determined by the angular velocity of a control shaft wherein the power required to rotate the control shaft to cause said transfer of power is less than the power transferred from the prime mover to the power output shaft, a feedback system comprising a rotary mechanical translating device driven by a prime mover and having a control shaft and a power output shaft, a differential having, a first and a second and a third shaft, a coupling means for coupling a portion of the power appearing in the power output shaft to the first shaft of the differential, said second shaft of the differential connected to the control shaft of the translating device and drive means for applying an external torque connected to the third shaft of the differential.
 2. A feedback system as claimed in claim 1, comprising at least a first and a last rotary mechanical translating device wherein the power output shaft of a preceeding translating device is connected to the control shaft of a succeeding translating device.
 3. A feedback system as claimed in claim 1 wherein the coupling means comprises torque sensing means for detecting the torque in the output shaft, and a variable speed transmission driven by the output shaft and connected to drive the first shaft of the differential, wherein the speed transfer ratio of said transmission means is responsive to said torque sensing means.
 4. A feedback system as claimed in claim 1 wherein the coupling means comprises torque sensing means for detecting the torque in the output shaft, and a variable speed transmission driven by the prime mover and connected to drive the first shaft of the differential, wherein the speed transfer ratio of said transmission means is responsive to said torque sensing means. 